Thief hatch

ABSTRACT

The disclosure provides systems and methods of manufacturing pertaining to an improved thief hatch. One embodiment provides a base, a cap, and an actuating mechanism disposed between the base and the cap. The base includes an annular lip that defines an opening that is configured to attach above an opening of a storage container such that the openings of the base and the container share a longitudinal center axis. The actuating mechanism is indirectly coupled to a seal such that in the resting position, the biasing mechanism exerts a biasing force on the seal toward the annular lip of the base to create a sealed connection. At least one structural constraint may protrude from the interior surface of the cap in a manner that prevents lateral movement of the actuating mechanism such that it moves exclusively along the longitudinal axis and cannot toggle during operation. Other embodiments are also disclosed.

BACKGROUND

Generally, storage containers such as above-ground or below-ground storage tanks include an opening to provide access to the interior of the tank. This opening may be designed to accept a venting device such as a thief hatch, which provides a re-sealable opening through which a thief or other tool may be inserted into the interior of the storage tank.

The internal pressure (e.g., internal vapor pressure) within a storage tank may fluctuate depending on various factors such as, for example, the amount of fluid in the tank, the volatility of the fluid in the tank, the temperature of the fluid in the tank, the ambient temperature outside the tank, a thermal conductivity of the walls of the tank, and so on. As vapor pressure in the storage tank increases, it often becomes necessary to relieve the pressure in a controlled fashion. In this regard, the thief hatch may provide a seal that blocks fluid communication between an interior of the storage tank and an exterior of the storage tank when the vapor pressure within the tank remains below a defined threshold but that enables or opens a path for fluid communication between the interior of the tank and the exterior of the tank once the vapor pressure within the tank exceeds the threshold.

Existing thief hatches or relief valves for storage containers exhibit a significant drawback in that the actuating mechanisms used to move a seal of the thief hatch between closed and open positions are capable of moving within multiple degrees of freedom. As a result, these actuating mechanisms tend to toggle during operation and often stick in an open position. Remaining open for long periods of time allows vapors and/or liquids (e.g., natural gas, oil, gasoline, etc.) to freely escape from the corresponding tanks. This excessive venting is unacceptable in many applications where tight sealing and controlled venting is key, such as, for example, in instances where strict environmental emissions standards are enforced.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter.

One embodiment provides a thief hatch configured to couple with a storage container having an opening. The thief hatch includes a base configured to affix to the storage container. The base has an annular lip that defines an opening, where the opening of the base and the opening of the storage container share a longitudinal center axis. The thief hatch also includes a cap coupled to the base, a seal disposed between the base and the cap, an actuating mechanism disposed on an interior surface of the cap, and at least one structural constraint. The actuating mechanism is configured to exert a biasing force on the seal to bias the seal against the annular lip of the base. In one embodiment, the structural constraint may be a pin configured to prevent lateral movement of the actuating mechanism such that the actuating mechanism moves exclusively along the longitudinal center axis.

Another embodiment provides a system for venting pressure from an interior of a storage container. The system includes a base having an annular lip that defines a central opening about a longitudinal axis. The central opening is configured to be in fluid communication with the interior of the storage container. The system also includes a cap rotatively coupled to the base and a seal assembly disposed between the base and the cap. The seal assembly includes a seal that is indirectly coupled to an actuating mechanism configured to exert a biasing force on the seal toward the annular lip, and the seal assembly is configured such that the actuating mechanism moves exclusively along the longitudinal axis between a closed position in which the seal blocks the central opening and an open position in which the seal is retracted from the central opening.

Yet another embodiment provides a method of manufacturing a thief hatch for coupling with a storage container, where the thief hatch includes a base with an annular lip that defines a central opening, a cap having exterior and interior surfaces, a seal disposed between the base and the cap, an actuating mechanism having first and second ends and in communication with the seal, and at least one structural constraint for limiting the movement of the actuating mechanism. The method includes the steps of (1) rotatively coupling the cap to the base; (2) enclosing the first end of the actuating mechanism within a structural insert configured to nest within a mating insert sleeve; (3) positioning the second end of the actuating mechanism within the insert sleeve such that the second end is disposed on the interior surface of the cap; (4) rotatively engaging a retention tab of the structural insert with a helical groove of the insert sleeve until the retention tab is retained within a longitudinal recess of the insert sleeve; and (5) affixing the structural constraint to the cap such that the structural constraint protrudes from the interior surface of the cap in a manner that prevents lateral movement of the actuating mechanism. The actuating mechanism may be a compression spring or any other appropriate biasing element.

Other embodiments are also disclosed, and additional objects, advantages and novel features of the technology will be set forth in part in the following description, and in part will become more apparent to those skilled in the art upon examination of the following, or may be learned from practice of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Illustrative embodiments of the invention are illustrated in the drawings, in which:

FIG. 1 illustrates a schematic of one embodiment of a storage tank system having an improved thief hatch;

FIG. 2 illustrates a top perspective view of one embodiment of an improved thief hatch;

FIG. 3 illustrates a cross-sectional view of the thief hatch of FIG. 2;

FIG. 4 illustrates a top perspective view of a pre-assembly insert sleeve of the thief hatch of FIGS. 2-3;

FIG. 5 illustrates a top perspective view of a post-assembly insert sleeve of the thief hatch of FIGS. 2-3;

FIG. 6 provides a flow diagram detailing an exemplary manufacturing process for the thief hatch of FIGS. 2-3;

FIG. 7 illustrates a front perspective view of the thief hatch of FIGS. 2-3 in a partially assembled state;

FIG. 8 illustrates a side perspective view of a seal assembly of the thief hatch of FIGS. 2-3 in a partially assembled state; and

FIG. 9 illustrates a bottom perspective view of the seal assembly of FIG. 8 in a partially assembled state.

DETAILED DESCRIPTION

Embodiments are described more fully below in sufficient detail to enable those skilled in the art to practice the system and method. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense.

Embodiments of the improved thief hatch described below provide an elegant solution to the excessive venting problems discussed above. In general, the described thief hatch provides a means to simply but precisely control the venting of fluids or vapors stored within a storage container or tank so as to ensure that the valve or seal opens when a pressure within the container reaches a defined threshold, but also promptly closes once sufficient pressure has been relieved and the pressure level within the container has returned to an acceptable level.

FIG. 1 provides a schematic of one embodiment of a storage tank system 10 having a storage tank 12 and an improved thief hatch 100. Storage tank system 10 may be a component of a variety of applications in a number of industries, including, but not limited to, the oil and gas, agricultural, and/or medical fields. Fluid or vapor stored within storage tank 12 may over time undergo an increase in pressure. In certain circumstances, it may become desirable to vent or release pressure from an interior 16 of storage tank 12 that is above a threshold pressure. To accomplish this release, storage tank 12 includes thief hatch 100, which is configured to periodically open fluid communication between interior 16 of storage tank 12 and an environment 18 external to storage tank 12 when the pressure within interior 16 of storage tank 12 exceeds a threshold pressure. In this manner, fluid or vapor may be vented from storage tank 12 as indicated by arrows 20. Once the internal pressure of storage tank 12 falls below the threshold pressure, the seal assembly of thief hatch 100 automatically closes and re-seals, thereby blocking fluid communication between the interior 16 of storage tank 12 and the external environment 18.

As discussed in greater detail below, thief hatch 100 includes various features to improve operation, performance, and reliability over existing thief hatches. For example, thief hatch 100 features an actuating mechanism that is physically constrained in its mobility. In this regard, thief hatch 100 may move between the open and closed positions exclusively along a longitudinal axis denoted by an axis Y. As detailed below, this constraint prevents a seal assembly of thief hatch 100 from toggling during operation and becoming stuck in an open position, which, if left unattended, leads to the over-venting of fluid or vapor from tank 12 into the environment.

FIGS. 2-3 illustrate respective top perspective and sectional views of one embodiment of improved thief hatch 100. Thief hatch 100 includes a cap 102 that is rotatively coupled to a base 104 via a biasing hinge 108 that biases cap 102 toward an open position. Cap 102 may be secured in a closed position via a releasable latch 106, which engages with a latch pin 109.

Thief hatch 100 may be mechanically installed on a storage tank (not shown) such that base 104 is disposed about an opening of the storage tank. Base 104 may be attached to the storage tank using bolts, rivets, welds, or any other suitable means and may include an annular lip 105 that defines an opening 107. Annular lip 105 lies concentric to the opening of the storage tank, and a longitudinal axis, Y, may intersect the common center of opening 107 and the opening of the storage tank.

In operation, thief hatch 100 is configured to seal the opening of the storage tank when in a closed position and expose the opening of the tank when in an open position. Whether the hatch 100 resides in a closed or open position is dependent upon an internal pressure within the tank. That is, thief hatch 100 remains closed unless and until the internal pressure within the tank reaches a threshold pressure, at which point thief hatch 100 opens to allow fluid communication between the interior of the tank and the ambient environment, thereby releasing pressure from the tank. Once the internal pressure within the tank returns to a point below the threshold level, thief hatch 100 returns to the closed position.

To accomplish this type of reliable venting, thief hatch 100 features a seal assembly 110 that includes a structural insert 112, an insert sleeve 114, and an actuating mechanism such as a compression spring 116. In this embodiment, the actuating mechanism is formed of a compression spring biased to its extended position. In other embodiments, the actuating mechanism may be a biasing element of any appropriate size, shape, type, material, and/or configuration.

Structural insert 112 may be configured to slidably nest within insert sleeve 114 in a way that fully envelops compression spring 116. In addition, structural insert 112 may include an annular pressure seal 115 that is adapted to form a sealed connection against annular lip 105 of base 104 when biased against annular lip 105. Together, structural insert 112 and insert sleeve 114 interact to manipulate compression spring 116 in a manner that causes the compression and decompression of spring 116. This compression and decompression translates to longitudinal movement of seal 115 along axis Y.

In further detail, a first end 118 of spring 116 may be disposed within structural insert 112, while a second end 120 of spring 116 may be disposed within insert sleeve 114 such that first end 120 abuts an interior surface 122 of cap 102. To accommodate the nesting of structural insert 112 within insert sleeve 114, sleeve 114 may include a set of helical grooves 124 and corresponding longitudinal recesses 126, shown in FIG. 4. Helical grooves 124 may serve as an assembly guide for retention tabs 128 (FIG. 3) of structural insert 112. In this regard, structural insert 112 may be positioned such that retention tabs 128 (FIG. 3) engage with helical grooves 124 and rotate clockwise until they disengage with helical grooves 124 and engage with longitudinal recesses 126 in an assembled position.

FIGS. 2-3 and 5 illustrate exemplary structural constraints that may be secured to cap 102 to constrain the movement of seal assembly 110 in a longitudinal direction along axis Y. In this embodiment, the structural constraints take the form of pins 130, which may protrude from interior surface 122 of cap 102 at each vertex 132 (FIG. 5) of helical grooves 124 and longitudinal recesses 126. Pins 130 secure retention tabs 128 within longitudinal recesses 126, thereby preventing any lateral movement of retention tabs 128 and structural insert 112 and, as a result, restricting the movement of compression spring 116 to a longitudinal direction along axis Y.

When spring 116 is compressed by rising pressure within the interior of the storage tank, retention tabs 128 slide upward within recesses 126 in a longitudinal direction denoted by arrow A in FIG. 3. This longitudinal movement causes seal 115 to retract from annular lip 105. This motion retracts seal 115 from annular lip 105 and opens fluid communication between the interior of the tank and the ambient environment. When the pressure on the interior of the tank decreases, spring 116 relaxes and retention tabs 128 slide downward in a longitudinal direction denoted by arrow B in FIG. 3. Seal 115 is, in turn, biased toward annular lip 105 to reestablish a sealed connection between the interior of the tank and the ambient environment. Because pins 130 prevent lateral movement of structural insert 112 and compression spring 116, there is no risk that structural insert 112 will partially slide free horizontal recesses 126 and into helical grooves 124 during operation. Thus, the opening and closing of seal assembly 110 remains consistently and predictably smooth.

In one embodiment, pins 130 may be formed of metal and threadably secured to cap 102. It should be understood that pins 130 may be any type of structural constraint of any appropriate size, shape, type, material, and/or configuration. In addition, pins 130 may be threadably connected, press fit, adhered, or attached to cap 102 in any appropriate and effective fashion.

Structural constraints such as pins 130 enable thief hatch 100 to precisely relieve pressure from the tank each and every time relief becomes necessary. Because the movement of structural insert 112 and compression spring 116 is restricted to a longitudinal direction along axis Y, these components cannot toggle or shift during operation. As a result, there isn't an opportunity for retention tabs 128 of structural insert 112 to slip out of longitudinal recesses 126 and into helical grooves 124 during operation. Thus, seal assembly 110 cannot stick in an open position even after sufficient pressure has been vented from the interior of the storage tank, and thief hatch 100 is able to operate consistently within a single, longitudinal degree of freedom to open fluid communication between the interior of the tank and the ambient environment only as necessary as dictated by the tank pressure level.

FIG. 6 provides a flow chart detailing an exemplary process 150 for manufacturing thief hatch 100. Process 150 initiates when cap 102 is rotatively coupled to base 104 (152) via biasing hinge 108. Biasing hinge 108 may incorporate or leverage a biasing element such as a torsion spring or other actuating mechanism configured to bias cap 102 toward an open position. Latch 106 may be used to counteract the force of biasing hinge 108 to retain cap 102 in a closed position as desired.

Once cap 102 has been attached to base 104, seal assembly 110 may be assembled. Thus, process 150 may continue with the positioning of first end 118 of compression spring 116 within structural insert 112 (154), as shown in FIG. 7. Next, and as shown in FIG. 8, second end 120 of compression spring 116 may be positioned within insert sleeve 114 (156) such that second end 120 is disposed upon interior surface 122 of cap 102. The steps of coupling cap 102 to base 104 (152) and positioning compression spring 116 within structural insert 112 and insert sleeve 114 (154 and 156) may occur in any desired or appropriate order.

Exemplary method 150 continues with the attachment of structural insert 112 to insert sleeve 114 in a manner that fully encompasses compression spring 116 within a shell formed of structural insert 112 and insert sleeve 114. To accomplish this, retention tabs 128 may be engaged with helical grooves 124 (FIG. 3) (158) and rotated in a generally clockwise direction until retention tabs 128 engage with longitudinal recesses 126 (160), resulting in a slidable coupling between structural insert 112 and insert sleeve 114 in which retention tabs 128 of structural insert 112 slide along longitudinal recesses 126. FIG. 9 illustrates a top perspective view of seal assembly 110 after structural insert 112 has been nested within insert sleeve 114.

After structure insert 112 has been coupled to insert sleeve 114, at least one structural constraint such as pin 130 may be affixed to cap 102 (162) such that pin 130 protrudes from interior surface 122 of cap 102 in a manner that prevents lateral movement of structural insert 112 and, in turn, compression spring 116. In one embodiment, pin 130 may be placed such that its edge aligns with a vertex 132 of helical groove 124 and longitudinal recess 126. As discussed above, pin 130 may be affixed to cap 104 in any appropriate manner, including a threaded connection, an adhered connection, a press fit, and so on.

Method 150 results in a seal assembly 110 that moves within one degree of freedom between the closed and open positions along longitudinal axis Y, thereby preventing any toggling of structural insert 112 and compression spring 116 during operation and preventing seal assembly 112 from becoming stuck in an open or partially open position. As a result, thief hatch 100 provides a safer, more precisely controlled, and more environmental friendly alternative to existing thief hatches or relief valves, which commonly stick in an open position and freely vent into the ambient environment.

Although the above embodiments have been described in language that is specific to certain structures, elements, compositions, and methodological steps, it is to be understood that the technology defined in the appended claims is not necessarily limited to the specific structures, elements, compositions and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed technology. Since many embodiments of the technology can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. 

1. A thief hatch configured to couple with a storage container having an opening, said thief hatch comprising: a base configured to affix to the storage container, said base comprising an annular lip that defines an opening, wherein said opening of said base and the opening of the storage container share a longitudinal center axis; a cap coupled to said base; a seal disposed between said base and said cap; an actuating mechanism disposed on an interior surface of said cap, said actuating mechanism configured to exert a biasing force on said seal to bias said seal against said annular lip of said base; and at least one structural constraint configured to prevent lateral movement of said actuating mechanism such that said actuating mechanism moves exclusively along said longitudinal center axis.
 2. The thief hatch of claim 1, wherein said cap is coupled to said base via a spring configured to enable said cap to rotate about said base between closed and open positions, and wherein said spring is configured to bias said cap toward said open position.
 3. The thief hatch of claim 2, wherein a latch releasably secures said cap to said base, and wherein said latch is configured to engage with a latch pin of said base when said cap is in said closed position.
 4. The thief hatch of claim 1, wherein said structural constraint comprises a pin protruding from said interior surface of said cap.
 5. The thief hatch of claim 4, wherein said actuating mechanism comprises a compression spring configured to generate said biasing force.
 6. The thief hatch of claim 5, further comprising: a structural insert configured to enclose a first end of said compression spring, said insert having at least one retention tab; and an insert sleeve protruding from said interior surface of said cap and configured to enclose a second end of said compression spring, said insert sleeve configured to receive and retain said structural insert such that said compression spring is nested therein, wherein said insert sleeve comprises a helical groove configured to guide said retention tab into a longitudinal recess adapted to retain said retention tab and allow said structural insert and said compression spring to move along said longitudinal center axis.
 7. The thief hatch of claim 6, wherein an edge of said pin aligns with a vertex of said helical groove and said longitudinal recess, thereby preventing movement of said structural insert and said compression spring in a lateral direction.
 8. The thief hatch of claim 6, wherein a height of said longitudinal recess defines a longitudinal travel distance of said compression spring and, therefore, of said seal.
 9. The thief hatch of claim 6, wherein said pin is installed on said cap via a threaded coupling, a press fit, or an adhered coupling.
 10. A system for venting pressure from an interior of a storage container, comprising: a base having an annular lip defining a central opening about a longitudinal axis, said central opening configured to be in fluid communication with the interior of the storage container; a cap rotatively coupled to said base; and a seal assembly disposed between said base and said cap, wherein said seal assembly comprises a seal indirectly coupled to an actuating mechanism that is configured to exert a biasing force on said seal toward said annular lip, and wherein said seal assembly is configured such that said actuating mechanism moves exclusively along said longitudinal axis between a closed position in which said seal blocks said central opening and an open position in which said seal is retracted from said central opening.
 11. The system of claim 10, wherein said actuating mechanism moves between said open and said closed positions in response to pressure fluctuations within the interior of the storage container.
 12. The system of claim 11, wherein said actuating mechanism comprises a compression spring, and wherein when said seal is in said open position, said compression spring is in a compressed state.
 13. The system of claim 12, wherein said seal assembly further comprises a structural constraint configured to limit movement of said compression spring to said longitudinal axis.
 14. The system of claim 13, wherein said structural constraint comprises a pin protruding from an interior surface of said cap.
 15. The system of claim 14, wherein said pin is installed on said cap via a threaded coupling, a press fit, or an adhered coupling.
 16. The system of claim 14, wherein said seal assembly further comprises a shell configured to enclose and manipulate said compression spring, said shell comprising: a structural insert having at least one retention tab and configured to enclose a first end of said compression spring; and a mating sleeve configured to receive a second end of said compression spring, wherein said sleeve includes a helical groove configured to guide said retention tab of said structural insert into a longitudinal recess adapted to retain said retention tab and allow said insert and said compression spring to move along said longitudinal axis.
 17. The system of claim 16, wherein an edge of said pin aligns with a vertex of said helical groove and said longitudinal recess, thereby preventing lateral movement of said structural insert and said compression spring. 18-20. (canceled) 